Australia will lead a new search for the wreckage of the missing Malaysia Airlines flight MH370 in an area 3,000 kilometres south-west of Perth, authorities announced today.

An unprecedented search operation has failed to find any trace of the plane, which went missing 11 days ago with 239 passengers on board.

The Australian Maritime Safety Authority (AMSA) says the search zone covers 600,000 square kilometres of ocean and has been plotted using data based on the last satellite relay signals sent by the plane.

Ships and aircraft from Australia, New Zealand and the United States will take part in the search, which represents a narrowing down of the previous Indian Ocean search area.

The same information has provided a mirror image of an area the same distance from the equator in the northern hemisphere .

Factbox: AP-3C Orion

Used for maritime surveillance, search-and-rescue operations and anti-submarine warfare

The southern search includes four Orion search planes from the RAAF, one New Zealand Orion, and a Poseidon operated by the US.

AMSA's emergency response general manager John Young said the search would be difficult because of the remoteness of the search area, warning it could take weeks.

"AMSA has defined a possible search area with information available to us from a range of sources both nationally and internationally," he said.

"This search will be difficult. The sheer size of the search area poses a huge challenge - the search area is more than 600,000 square kilometres.

"AMSA holds great concerns for those on the flight but is working positively ... as part of international efforts."

Mr Young said the search area was based on information provided by the US National Transportation Safety Board, which was collected on Malaysia's behalf.

"The area where the aircraft might have entered the water was corrected for water movement over the elapsed time by the Rescue Coordination Centre in Canberra to provide a possible search area that is relevant to efforts today," he said.

"Every attempt will be made to further refine the search area as further information becomes available.

"This includes further analysis of drift modelling and other search tools, but with the passage of significant time since March 8 [when the plane disappeared], and with the constant movement of water, that'll be constantly difficult."

Searching for 'a needle in a haystack'

Mr Young said one RAAF Orion aircraft is searching the area and is due back in Perth later today.

"It is expected due to the distance offshore that the aircraft will search only a small portion of the defined area," he said.

"Ships in the southern Indian Ocean have also been requested to keep a lookout for anything relevant to the search and to travel through the search area if possible.

"One ship is presently travelling through the area and another has reported it will pass through the area later today."

Mr Young says that "a needle in a haystack remains a good analogy" and that the search could be ongoing for weeks.

"We are taking this search very seriously. I am describing it as a possibility. The aircraft could have gone north or south," he said.

"Our purpose is firstly to find anyone alive if there is anyone to be found [and] secondly to prove or discount the possibility that the aircraft came south - to do that would be a significant development in the search."

Prime Minister Tony Abbott told Question Time today that Australia would continue to do all it could to find the missing aircraft.

The swell is three metres at the moment, gusts of 25 kilometres an hour. None of these planes can actually see below the ocean, of course, so they're really just looking for debris on top of the surface. The longer it goes from the time it went missing, the harder you would think that it is going to be to locate.

ABC defence correspondent Michael Brissenden

"We owe it to the people on this ill-fated flight and their families to do what we can to solve this tragic mystery," the Prime Minister told Parliament.

Mr Young said AMSA was in contact with China, which would also like to be a part of the search.

Investigators believe the plane could have flown in one of two different directions after its tracking systems were turned off - one north-west into Asia and another path south-west into the Indian Ocean.

China has meanwhile begun searching for the missing jet in its own territory in the possible northern flight corridor, Chinese state media said, citing Beijing's envoy in Kuala Lumpur, Huang Huikang.

State media also quoted Mr Huang as saying no evidence has been found linking the 153 Chinese passengers aboard the missing flight to terrorism or hijacking.

Family of passengers, US criticise Malaysia's search

Meanwhile, the Malaysian official in charge of the search has rejected criticism from US officials that it has not been sharing enough information with foreign governments.

China has called for better coordination in the search operation now involving 26 countries, while some US officials and politicians have expressed frustration at what they see as Malaysia's refusal of help.

Malaysian defence minister Hishammuddin Hussein specifically defended coordination with the US and China and said he had been in touch with his counterparts in both countries.

"This morning, I was [speaking] with [US defence secretary] Chuck Hagel and then I was also with my counterpart [from] China," he told the Reuters news agency.

Mr Hishammuddin also denied reports that Malaysia had discouraged the FBI from sending a team to Malaysia.

"I have been working with them. It's up to the FBI to tell us if they need more experts to help because it's not for us to know what they have," he said.

Malaysian officials say they have been in touch with the FBI through the US embassy, where the agency has a permanent representative, from "day one".

Authorities are also under pressure from desperate relatives of Chinese passengers who have threatened to go on a hunger strike in protest against the lack of information on the search.

Two-thirds of the passengers on the flight were Chinese.

Outside a gathering of families of missing passengers, a woman clutching a placard reading "Respect life. Give us back our families" told reporters that the relatives were going on hunger strike.

"Since they haven't given us the truth about those people's lives, all of us are protesting," the woman said.

"All the relatives are facing mental breakdowns."

Wen Wancheng, whose son was on board the missing flight, said some of the relatives had stopped going to the meetings, given how long they had been waiting for information.